This invention relates to a coolant purification system and more particularly to an improved arrangement for purifying coolant utilized in machining operations.
As is well-known, many types of machining operations are utilized in conjunction with a cooling system wherein some form of liquid coolant is supplied to the machining apparatus. The coolant performs a number of functions. First and as its name implies, the function of the liquid coolant is to cool the heat that is generated by the machining operation so as to avoid over-temperature of the workpiece. In addition, the coolant serves the purpose of flushing the machined particles away from the machining area so as to improve surface finish. That is, if the particles are not removed from the machining area, they can cause surface imperfections.
Thus, the supply of coolant and its treatment is obviously an important factor in ensuring good machining. However, it is also desirable to ensure that the coolant can be recirculated so that it will not be spent and cause environmental and disposal problems. Therefore, a variety of types of devices have been employed for removing the machining particles and other foreign material from the coolant so that it can be recirculated.
FIG. 1 shows a conventional type of prior art machining apparatus having an arrangement for recycling and purifying the coolant. As seen in this Figure, there is provided, at an appropriate location, a coolant storage tank, indicated generally by the reference numeral 21 in which a liquid coolant of a suitable type, indicated at Co, is stored. This coolant Co is utilized at a machining station, indicated generally by the reference numeral 22, for the aforenoted purposes. That, it is employed for removing particles from the machining area and also cooling the machining operation.
As an example, the machining apparatus can include a machine tool such as a shaving cutter 23 that operates on a workpiece W to perform surface machining thereon.
This workstation 22 also includes a tray area 24 which underlies the machining station 23 in which the coolant which is circulated, in the manner to be described shortly, is accumulated and returned back to the coolant storage tank 21 after passing through a purification or filtering section, indicated generally by the reference numeral 25.
A first pump 26 has a pick-up 27 that depends into the coolant storage tank 21 and pumps it through a conduit 28 in which a manually operated flow control valve 29 is positioned. The conduit 28 delivers the coolant to a suitable shroud 31 that encircles the machining station 22 and specifically the tool 23 for washing and cooling the workpiece W and the cutting apparatus 23.
In addition, a second pump 32 also picks up cooling fluid Co from the tank 21 through a pickup tube 33. This coolant is delivered by means of a spray nozzle 34 at the end of a conduit 35 to the tray 24. This serves the function of flushing the collected coolant and machining particles and other foreign material to a pair of drain passages 36 and 37 which convey the fluid to a tank 38 of the purifying or filtering apparatus 25.
The filtering or purifying apparatus 25 is generally of the magnetic separator type having a Ferro magnetic separator 39 which collects the fluid from the tank 38 and separates particles through a chute 41 to a discharge tank 42 which must be cleaned and emptied periodically. The remaining fluid is returned to the storage tank 21 through a return conduit 43. This type of separator is generally only effective in removing particles having a size of 100 .mu.m or greater.
In addition to the coolant Co, there is frequently oil or other lubricant in the machining operation. This other light fluid collects the particles and causes them to float in a layer indicated at 44 on top of the coolant Co in the tank 23. Normally, there is provided a separating wall 45 between the return area and the area where the pump pickups 27 and 33 are located. This is done to reduce the likelihood of picking up these floating particles. Some of the particles will precipitate in the tank 21 in this area as seen at 46. A further lower baffle wall 47 is provided inwardly from the wall 45 so as to separate these particles from the pickups 27 and 33.
There are a number of defects with this type of system. In addition to the fact that only relatively large particles are separated, the magnetic separator device 39 is generally capable of only catching about 50% of the magnetic particles contained in the circulated coolant. The remaining particles including non magnetic ones, therefore, will either float in the area 44, be solidified in the area 46 or remain entrained in the coolant and thus, continue to be circulated.
These particles can cause, as will become apparent later by reference to FIGS. 3-5 poor surface finishes. Also, during shutdown, further precipitation in the area 46 will occur and frequently it is necessary to clean the tank after periods of non use.
It is, therefore, a principal object of this invention to provide an improved and effective way of filtering or cleaning a cooling fluid for a machining operation.
It is a further object of this invention to provide an improved arrangement for purifying cooling fluid and minimizing the amount of servicing required for the apparatus.
There are obviously other types of filtering or liquid cleaning devices that can have the ability to remove particles that have a smaller size than the magnetic type of separator. However, generally the higher the filtering capability, i.e., the ability to remove smaller particles, the more frequently the filter has to be serviced. Of course, this problem can be reduced to some extent by using large filters, but then the cost and size of the overall apparatus becomes a problem.
In addition, in order to preserve the filter life, it is generally necessary to manually clean the filter. This is not only a time-consuming and labor-intensive operation, but it also is not a very pleasant task. Furthermore, the problem of disposal of the contaminants also presents certain problems.
It is, therefore, a still further object of this invention to provide an improved coolant purifying system for a machining operation for purifying liquid coolant which will provide a high degree of filtration and which will not necessitate frequent servicing.
It is a further object of this invention to provide an improved coolant purifying system that operates over long time periods without requiring servicing and without diminishing the coolant flow.
It is a further object of this invention to provide an improved arrangement for cleaning a filter for a coolant purifying system wherein manual operations are substantially reduced or totally eliminated.